Hey TommyB,
We have not done the excursion you mention, however, we are also going to St. Thomas in April and are planning on going to Coral Park. We have a group of 7 going and some want to Snuba while others want to Parasail and it seems Coral Park has it all (including a beach for those who just want to worship the sun and the sand). Sorry but I don't remember the exact website (maybe www.coralparkvi.com) if you want to check it out. Hope you have a blast! 8)